Pluggable optical transceiver and method for manufacturing the same

ABSTRACT

A pluggable optical transceiver is disclosed. The transceiver comprises a plurality of OSAs, an optical member and a plurality of inner fibers to couple the optical member with OSAs. The inner fibers each provides an inner connector to couple with one of OSAs. The housing, which installs the OSAs, the optical member and the inner fiber, is made of metal and has a grooves into which the inner fibers is set so as to arrange them orderly.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional patentapplication Ser. No. 61/261,105 filed Nov. 13, 2009, and Ser. No.61/314,801 filed Mar. 17, 2010, which are incorporated herein byreferences.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pluggable optical transceiver with afunction of at least one of the optical transmission and the opticalreception, in particular, the invention relates to an opticaltransceiver able to transmit a plurality of optical signals each havinga specific wavelength different from others, and to receive a pluralityof optical signals each having a specific wavelength different fromothers.

2. Related Background Art

The United States patent, U.S. Pat. No. 5,943,461B, has disclosed anoptical transceiver providing an optical connector coupled with anoptical plug attached in a tip of the external fiber. An optical fiberis drawn from the optical connector to couple with an opticalsubassembly (hereafter denoted as OSA) that installs a semiconductordevice, such as semiconductor laser diode (LD) for a transmitter OSA(TOSA) or a semiconductor photodiode (PD) for a recover OSA (ROSA).

The transmission speed of the optical communication has been acceleratedand the transmission speed over 10 Gbps, typically 40 Gbps and 100 Gbps,is now available. The semiconductor device in the OSA is quite hard tofollow such high speed alone. The intelligent system of the wavelengthdivision multiplexing (WDM) is ordinarily applied. For instance, foursignal channels each showing the speed of 10 Gbps and having a specificwavelength different from others are wavelength multiplexed, whichequivalently shows the transmission speed of 40 Gbps, and thusmultiplexed optical signal is transmitted in the single optical fiber.In the system with the speed of 100 Gbps, four (4) signal channels eachhaving the speed of 25 Gbps are multiplexed or ten (10) signal channelseach showing the speed of 10 Gbps are multiplexed to realize theequivalent transmission speed of 100 Gbps. One agreement,CFP-MSA-Draft-rev-1.0, has specified the standard of the 100 Gbpstransmission.

An optical transceiver satisfying the WDM standard installs a pluralityof TOSAs and ROSAs, an optical multiplexer and an optical demultiplexer.Another type of an optical transceiver for the WDM communicationinstalls an optical unit integrating a plurality of TOSAs with anoptical multiplexer and another optical unit integrating a plurality ofROSAs with an optical demultiplexer to eliminate or to decrease thenumber of inner fibers connecting the optical components. However, suchan integrated optical device has a demerit that the whole component isnecessary to be replaced even when only one of the TOSAs or only one ofthe ROSAs becomes failure. In particular, the TOSAs and the ROSAsoperable in such high speed region are hard to be available, or oftenhave a restricted margin for the specification; a situation to replace adegraded OSA would be often encountered.

For the optical transceiver installing TOSAs and ROSAs individually,inner fibers coupling each component are scattered. Moreover, theoptical fiber has an inherent characteristic to increase thetransmission loss by the bending. Conventional optical fiber limits theleast bent radius of 15 mm. Even an improved fiber limits the minimumbent radius to be 5 mm. Thus, a surplus length is necessary to beprepared for the inner fibers, which means that lengthy fibers runwithin the optical transceiver disorderly without adequate wiring of theinner fibers.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to an optical communicationapparatus for the WDM communication system. The apparatus comprises aplurality of optical components, an electronic component, a plurality ofinner fibers and a housing. The optical components include an opticalreceptacle, a plurality of OSAs, and an optical unit. The OSAs may beTOSAs or ROSAs, while, the optical unit may be an optical multiplexer oran optical demultiplexer depending on the type of OSAs. The multiplexermay multiplex a plurality of optical signals each transmitted fromrespective TOSAs and having a specific wavelength different from others.The optical demultiplexer may demultiplex a optical signal externallyprovided into a plurality of optical signals each having a specificwavelength different from others; and transmits demultiplexed opticalsignal to respective ROSAs. The electronic component includes a circuitmounted on a circuit board and electrically coupled with the TOSAs andROSAs. The inner fibers may optically couple the optical receptacle withthe optical multiplexer and the optical demultiplexer; and couple theoptical multiplexer with the TOSAs and the optical demultiplexer withthe ROSAs. The housing may install the optical components, theelectrical components and the inner fibers therein. One feature of thecommunication apparatus according to the present invention is that thehousing is divided into two sections, one of which installs only theoptical components, while, the other installs only the electroniccomponents, and the inner fibers may be coupled with optical componentsin the pluggable form.

Because the housing is distinguishably divided into two sections, theinner fibers may run under the optical components in the one section andunder the circuit board in the other section. The optical components mayfurther include a plurality of inner connectors, a front tray and alatch unit. Each inner connector is provided in or associated with theend of the inner fiber and coupled with OSA in the pluggable form. Thefront tray may support the inner connector and arrange the inner fiber.The latch unit may support the OSA and may be coupled with the innerconnector in two positions.

The front tray may provide a plurality of slots. Each of the slots mayreceive one of inner fibers and provide a pair of latch fingers toengage with the inner connector. The slot may further provide an eave toprevent the fiber set therein from straying out and a guide in a sidethereof to turn the inner fibers running the side of the front tray fromthe longitudinal direction to the lateral direction.

The communication apparatus of the present invention may further providea rear tray under the circuit board in the other section of the housing.The rear tray may also guide the inner fiber drawn from the one sectionso as to head to the one section again. The rear tray may also provide aplurality of eaves to prevent the inner fiber set therein from strayingout.

The one section of the housing of the present communication apparatusmay provide a plurality of terraces for mounting the optical componentsthereon, where the terraces may form a plurality of grooves to set theinner fibers therein; and the other section of the housing may alsoprovide a plurality of terraces whose outer periphery may define a bentcurvature of the inner fibers. The terraces in the other section maycome in contact with the circuit mounted on the circuit board to securea heat dissipating path from the circuit to the housing.

The grooves formed in the terraces of the one section may provide twopairs, the first pair of which has a distance between the groovessubstantially equal to a distance between two fibers in the SC-typeoptical receptacle; while, the second pair of grooves has anotherdistance therebetween which is substantially equal to a distance betweentwo fibers in the LC-type optical receptacle. Accordingly, when theoptical receptacle of the present communication apparatus is theSC-type, the inner fibers drawn from the optical receptacle may be setin the first pair of grooves, while, when the LC-type optical receptacleis installed, the second pair of the grooves may receive the innerfibers drawn from the optical receptacle.

The housing of the present optical communication apparatus may providean area to mount the optical receptacle thereon. The area may bepartitioned from the one section by the rear wall and the side walls.The optical receptacle may be mounted in this area as putting anelectrically conductive sheet between the rear of the optical receptacleand the rear wall, which may shield the one section and the othersection from the exterior effectively.

Another aspect of the present invention relates to a method to assemblethe optical communication apparatus. The apparatus comprises the opticalcomponents, the electrical components, a plurality of inner fibers, anda housing. The optical components include an optical receptacle, anoptical unit, and a plurality of OSAs, while, the electrical componentsinclude an electronic circuit mounted on a circuit board. The innerfibers each couples one of the OSAs with the optical unit; and thehousing installs these optical components only in the one section and,electrical components in only in the other section different from theone section, and the inner fibers. The method of the invention maycomprise steps of: (a) installing the optical unit within the housing,(b) arranging the inner fibers extended from the optical unit; (c)installing the circuit board, which is assembled with OSAs, into thehousing so as to cover the inner fibers; and (d) coupling the OSAsoptically with the inner fibers.

One feature of the present method is that the inner fibers may beoptically coupled with the OSAs after arranging the inner fibers withinthe housing and installing the OSAs into the housing. The step ofarranging the inner fibers may include steps of: (b-1) setting the innerfibers in the grooves formed in one section of the housing, where theone section installs only the optical components; and (b-2) bending theinner fibers along a periphery of the terrace formed in the othersection of the housing, where the other section installs only theelectronic components. Moreover, the step of installing the circuitboard may include step of: (c-1) covering the inner fibers set in thegrooves and bent along the periphery by the circuit board.

In a modification, the step of arranging the inner fibers may includesteps of: (b-1)′ setting a rear tray in the other section of thehousing; and (b-2)′ bending the inner fibers with a curvature defined bythe rear tray; and the step of installing the circuit board may includea step of: mounting the circuit board on the rear tray so as to coverthe inner fibers set in the rear tray.

In the process of the invention, the step of arranging the inner fibersmay include steps of: (b-1) covering the inner fibers by a front trayand a latch unit to be mounted in the one section of the housing, (b-2)guiding each of the inner fibers in one of slots of the front tray; andthe step of installing the circuit board may include steps of (c-1)coupling the inner connector attached to an end of the inner fiber withthe front tray, (c-2) setting the inner connector in a retreatedposition, (c-3) mounting the latch unit in the one section of thehousing, and (c-4) installing the OSAs assembled with the circuit boardin advance on the latch unit; and the step of coupling the OSAs with theinner fibers may include step of setting the inner connector in acoupling position.

Still another aspect of the present invention relates to an opticaltransceiver that comprises an OSA, an inner fiber that provides in oneend thereof, a ferrule, an elastic member and a flange, a tray to guidethe inner fiber, and an inner connector. The inner connector of thepresent optical transceiver, which receives the one end of the innerfiber, is assembled with a stopper to hold the elastic member within theinner connector, is movably supported by the tray, and is engaged withthe OSA through the latch unit. A feature of the present opticaltransceiver is that the inner connector is movable between a retreatedposition and a coupled position. In the coupled position, the ferrulemay be optically coupled with the OSA, while, the inner connector doesnot interfere with an installation of the latch unit pre-assembled withthe OSA at the retreated position.

The inner connector of the invention may provide a groove to receive alatch finger of the tray, where the groove may provide projection todetermine the retreated position and the coupled position. In anexample, the groove may provide two projections, and the retreatedposition may be determined between the deeper side projection and theend wall of the groove, while, the coupled position may be set betweentwo projections. In another example, when the groove provides threeprojections, the retreated position may be set between the deepestprojection and the end wall, while, the coupled position may bedetermined between the shallower two projections.

The inner connector of the invention may provide the first portion toreceive the inner fiber, the second portion to receive the elasticmember and the flange, and a partition wall to divide the first andsecond portions. The elastic member may be set between the partitionwall and the flange; accordingly, the ferrule is pushed out from thestopper.

Still another aspect of the present invention relates to an opticaltransceiver that comprises a resin made optical receptacle, a housingand an electrically conductive sheet. The optical receptacle may includea sleeve assembly to output an inner fiber with the pig-tailedarrangement. The housing provides an area to install the opticalreceptacle thereon. This area may be surrounded by the side walls andthe rear wall. The conductive sheet may be put between the opticalreceptacle and the rear wall.

The sleeve assembly may further include first and second cylinders, anda flange between the cylinders. The inner fiber is output from thesecond cylinder in the pig-tailed arrangement. The first cylinderprotrudes into a cavity of the optical receptacle by passing through theconductive sheet. The optical receptacle may provide a rear wall, whichpushes the conductive sheet against the rear wall of the housing, with astep to receive the flange of the sleeve assembly. The housing mayfurther provide a face cover to push the optical receptacle against therear wall of the housing as sandwiching the conductive sheet.

A feature of the optical receptacle is that it may provide a lug inrespective sides thereof, while, the side wall of the housing mayprovide a pocket that receives the lug. The lug is attached to the sideof the receptacle in one end thereof, and bent vertically from theattached portion. The bent portion may be elastically rotate around theattached portion, which may further push the conductive sheet againstthe rear wall of the housing. The lugs in both sides of the opticalreceptacle may be diagonally formed, and the pockets in respective sidewalls may be also diagonally formed. The lug may provide a rib crushableby abutting against the wall of the pocket. The conductive sheet may bea non-woven fabric, or may be made of rubber coated with an electricallyconductive material that comes in contact with the rear wall of thehousing.

The rear wall of the housing may provide pair of double cuts. One of thepaired cuts may have a pitch equal to a pitch between two optical axesof the SC-connector, while the other paired cuts may have another pitchequal to a pitch between two optical axes of the LC-connector. Theoptical receptacle of the present invention may be applicable to theSC-type optical connector and the LC-type optical connector.

The optical receptacle may provide a plurality of bosses in the rearwall thereof. The bosses may abut against the conductive, thus, theconductive sheet may securely come in contact with the rear wall of thehousing. The bosses may be provided in whole outer surface of theoptical receptacle. When the housing of the present optical transceivercomprises an upper housing and a lower housing, where the opticalreceptacle is put between these housings, the bosses in the outersurface of the receptacle housing may come in contact with the upper andlower housings, which may effectively and reliably shield the opticaltransceiver.

Moreover, the optical transceiver of the present invention may provide ashield gasket put between the upper and lower housings, in particular,the shield gasket may be put on the side walls and rear walls formed inlower housing so as to surround the area where the optical receptacle ismounted. The shield gasket may not only come in contact with the upperand lower housings, but in contact with the conductive sheet between therear of the optical receptacle and the rear wall, which may shield theoptical transceiver in further effective and reliable.

According to another aspect of the optical transceiver of the presentinvention, the optical transceiver comprises a plurality of OSAs, acircuit board, a plug board, and a housing. The circuit board mounts anelectronic circuit coupled with the OSAs thereon. The plug boardprovides an electronic plug which mates with the host connector. Theplug is electrically connected with the circuit through an electricalconnector set between the plug board and the circuit board. A feature ofthe optical transceiver of the invention is that the plug board isrigidly supported by the housing; while, the circuit board is softlysupported by the housing. The housing may comprise the upper housing andthe lower housing, where the plug board is put between the upper andlower housings, and the circuit board is also put between the upper andlower housings but through gaskets.

The plug board may provide a rib in both top and back surfaces thereof,while the upper and lower housings each provides a groove to receive therib in the plug board. A metal cover, whose shape may trace the shape ofthe rib, may be interposed between the rib and the groove. The metalcover may provide a plurality of legs and fins each coming in contactwith and pushing the walls of the groove. Thus, the plug board may berigidly supported by the upper and lower housings.

On the other hand, the circuit board may provide ground patterns in sideportions of top and back surfaces thereof. The baskets may come incontact with the ground pattern. The ground patterns in the front andback surfaces formed in the same side portion of the circuit board maybe connected with a via holes or an enveloping pattern covering the edgeof the circuit board, which may effectively shield the circuit mountedon the circuit board. The upper and lower housings may provide a groovein a side portion thereof to receive respective gaskets. In amodification, the gasket may be a U-shaped metal member with a slabportion and a pair of legs. The slab portion may envelope the edge ofthe circuit board, while, the legs may provide fins that come in contactwith the upper and lower housings. Even the gasket has the arrangementabove described, the upper and lower housings may softly put the circuitboard therebetween, and effectively shield accompanied with the gasket,the circuit on the circuit board.

Still another aspect of the present invention relates to a pluggableoptical transceiver that is plugged with the host system and have adistinguishable feature that the optical transceiver may be preventedfrom being released from the host system when the optical transceiverreceives the external connector in the optical receptacle thereof, and,in addition to the specific function described above, the opticaltransceiver of the present invention may be also prevented fromreceiving the external connector when the optical transceiver is freefrom the host system, that is, when the optical transceiver is notplugged with the host system.

The optical transceiver of the invention comprises an optical receptacleto receive the external connector, a screw latch to engage the opticaltransceiver with the host system, a latch bar to show the mechanismdescribed above and a housing to install the optical receptacle, thescrew latch and the latch bar. That is, the latch bar may protrude inone end thereof into the optical receptacle when the optical receptacleis vacant, while, the screw latch may provide a groove to receiveanother end of the latch bar.

In an original position of the optical transceiver, where the opticaltransceiver is free from the host system, the screw latch pushes theother end of the latch bar, accordingly, the one end of the latch barmay protrude into the optical receptacle, where the optical receptacleis prevented from receiving the external optical connector. When theoptical transceiver is engaged with the host system by fastening thescrew latch to the host connector, the other end of the latch bar mayalign with the groove of the screw latch, which makes a rest space toreceive the other end of the latch bar. Inserting the external connectorinto the optical receptacle, the external connector may push the one endof the latch bar and the other end of the latch bar may be set withinthe groove of the screw latch. Thus, the external connector may beengaged with the optical receptacle only when the optical transceiver isplugged with the host system. Moreover, because the other end of thelatch bar is received in the groove of the screw latch, the screw latchmay be prevented from disengaging with the host connector by the latchbar operating as a stopper, the optical transceiver may be preventedfrom being released from the host system.

The latch bar may provide an elastic portion, while the housing mayprovide a space to receive the elastic portion therein. The latch barmay automatically recover the original position thereof by the elasticforce caused by operation of the elastic portion within the space.Moreover, the optical receptacle may provide a cut to pass the one endof the latch bar. The latch bar may protrude into the optical receptaclethrough the cut.

Still another aspect of the present invention relates to a connectorassembly to be set within a pluggable optical transceiver. The connectorassembly may comprise a latch unit, an inner fiber, and a connectorhousing. The latch unit supports the OSA and includes a pair of latchfingers. The inner fiber has, in an end portion thereof, a ferrule, aflange, and a coil spring with an end abutting against the flange. Theconnector housing may comprise first and second spaces, and a centerpartition that distinguishes said first space from said second space.The first space receives the end portion of the inner fiber as the otherend of the coil spring abuts against the center partition. The secondspace secures the inner fiber continuous to the end portion. A featureof the connector assembly of the present invention is that the firstspace of the connector housing is engaged with the latch finer of thelatch unit to couple the inner fiber optically with the OSA. The firstspace of the connector housing may provide a pair of side latches eachsupported by the center partition. The side latch may have a U-shapedcross section within which the latch finger of the lath unit may besecured to engage therewith.

The connector assembly of the invention may further provide a ferrulestopper that is supported by the connector housing so as to put theferrule, the flange, and the coil spring between the ferrule stopper andthe center partition. Thus, the inner fiber and the connector housingmay be prevented from disassembling. The ferrule stopper may provide abeam and a pair of legs each extending from the beam so as to form theU-shaped cross section. The beam may have an opening through which theferrule passes, and the flange in a root of the ferrule may abut againstthe beam. The legs may provide a tab to be latched with the connectorhousing. Accordingly, the ferrule, the flange, and the coil spring maybe prevented from disassembling with the connector housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other purposes, aspects and advantages will be betterunderstood from the following detailed description of a preferredembodiment of the invention with reference to the drawings, in which:

FIGS. 1A and 1B show an optical transceiver according to an embodimentof the present invention, where FIG. 1A views the optical transceiverfrom upper front, while, FIG. 1B views the optical transceiver from rearbottom;

FIG. 2 is an exploded view of the optical transceiver;

FIG. 3 views a host system to which the optical transceiver shown inFIG. 1 is to be mounted;

FIG. 4A shows the inside of the first housing, while, FIG. 4B shows theinside of the second housing;

FIG. 5A magnifies a front portion of the inside of the opticaltransceiver, and FIG. 5B is a cross section thereof;

FIG. 6A illustrates another type of housing that mounts a rear tray, andFIG. 6B shows the rear tray to which inner fibers are set;

FIG. 7A is a perspective view showing the circuit board 18 and the plugboard 19, FIG. 7B shows the circuit board 18 without any componentsthereon, FIG. 7C shows a cross section of a side edge portion of thecircuit board, and FIG. 7D shows the plug board 19;

FIG. 8A is a horizontal cross section of the optical transceiver showingthe circuit board and the gasket put between the housings, FIG. 8Bmagnifies a side portion of the circuit board shown in FIG. 8A, and FIG.8C illustrates a modified ground pattern provided on the circuit board;

FIG. 9A is a perspective view showing another type of a gasket putbetween two housings, and FIG. 9B is a horizontal cross section showinga side portion of the circuit board and the modified gasket shown inFIG. 9A;

FIG. 10A shows a metal cover, FIG. 10B shows a modified metal cover, andFIG. 10C is a cross section showing the metal cover, the grooves in thefirst and second housings, and the ribs in the plug board;

FIG. 11A illustrates the optical multiplexer and inner fibers extendedtherefrom, and FIG. 11B illustrates the sleeve assembly set in theoptical receptacle;

FIG. 12 is a perspective view showing the front tray according to anembodiment of the present invention;

FIG. 13A is a perspective view showing a front tray according to anotherembodiment of the present invention, and FIG. 13B shows a front portionof the optical transceiver that installs the front tray shown in FIG.13A with inner fibers in respective slots of the front tray;

FIG. 14 is a perspective view showing the inner connector coupled withthe latch unit;

FIG. 15A shows the inner connector viewed from the rear, while, FIG. 15Bshows the inner connector viewed from the front;

FIG. 16A is an exploded view of an inner connector according to anotherembodiment of the present invention, FIG. 16B shows the assembled innerconnector shown in FIG. 16A, FIG. 16C shows a connector body, and FIG.16D is a cross section showing the inner connector illustrated in FIG.16B engaged with the latch finger of the front tray;

FIG. 17 is a perspective view showing another type of the innerconnector;

FIG. 18A shows a latch unit according to an embodiment of the presentinvention, and FIG. 18B shows a latch unit according to anotherembodiment of the present invention;

FIG. 19A is a side view of an OSA, and FIG. 19B is a rear view of oneslot of the latch unit;

FIG. 20 is a cross section taken along the optical axis of the innerfiber set in the inner connector;

FIG. 21A is a perspective view showing a front portion of the firsthousing according to another embodiment of the present invention, andFIG. 21B is a front view thereof;

FIG. 22A views an optical receptacle according to an embodiment of theinvention, which is viewed from the rear, FIG. 22B views the opticalreceptacle from the front, and FIG. 22C is an exploded view of theoptical receptacle;

FIG. 23 shows a process to mount the optical receptacle in the centerarea of the first housing;

FIG. 24 shows a face cover attached to the housing;

FIG. 25 shows an optical receptacle according to another embodiment ofthe invention, where the optical receptacle shown in FIG. 25 has the LCtype configuration;

FIGS. 26A and 26B show an optical receptacle according to still anotherembodiment of the invention;

FIG. 27 shows a screw latch according to an embodiment of the presentinvention;

FIG. 28 explains a structure prepared in the housing for setting thescrew latch shown in FIG. 27;

FIG. 29 is a perspective view showing a latch bar according to anembodiment of the present invention;

FIGS. 30A and 30B are a cross section and a front view, respectively, ofthe latch bar and the screw latch when the optical receptacle is freefrom the external connector, while, FIGS. 30C and 30D are a crosssection and a front view, respectively, of the latch bar and the screwlatch when the optical receptacle receives the external connector;

FIGS. 31A to 31D show the processes to wire the inner fibers;

FIG. 32 shows a process to set the inner fiber into the front tray;

FIG. 33A shows a process when the inner connector in a position able tocouple with the OSAs, while, FIG. 33B shows a process when the innerconnector in another position not to interfere the OSAs; and

FIG. 34 shows a process to mount the OSAs and two boards of the circuitboard and the plug board on the housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, some preferred embodiments according to the present invention willbe described as referring to accompanying drawings. In the descriptionof the drawings, the same numerals or symbols will refer to the sameelements without overlapping explanations.

First Embodiment

FIGS. 1A and 1B are perspective views of an optical transceiver 1according to an embodiment of the present invention, where FIG. 1A viewsthe optical transceiver 1 from upper front, while FIG. 1B views thetransceiver from rear bottom. In the description presented below, thefront side corresponds to a side where an optical receptacle 14 isimplemented, the rear side corresponds to a side where an electricalplug 19 b is installed, the upper or the top corresponds to a side wherethe first housing 10 a is installed with respect to the second housing10 b, and the lower or the bottom corresponds to the side the secondhousing 10 b is implemented. FIG. 3 illustrates the host system on whichthe optical transceiver 1 is to be mounted. The host system 2 typicallyprovides the system board 2 a, where a pair of rails 3 b and the hostconnector 3 a is mounted. The face panel 2 b with a port 2 c is providedin the host board 2 a. The optical transceiver 1 of the presentinvention may be pluggable with the host connector 3 a by inserting itfrom the port 2 c.

The optical transceiver 1 illustrated in FIGS. 1 and 2 provides ahousing 10 with a size of 128×72×14 mm³, which is decided by amulti-source agreement concerning to, what is called as, the CFPtransceiver. The housing 10 of the embodiment is made of metal.

The optical transceiver 1 provides a face cover 12 in the front end ofthe housing 10. An optical receptacle 14 is assembled in a centerportion of the face cover 12 with screws. The housing 10 also provides apair of screw latches 16 in both ends of the face cover 12. Front end ofthe screw latch 16 provides a knob 16 a extended from the face cover 12,while the rear end of the screw latch 16 is formed with a thread 16 b.This thread 16 b is to be fastened with a tapped hole provided inrespective sides of an electrical connector 3 a prepared in the hostsystem 2; thus, the optical transceiver 1 is to be fixed to the hostsystem 2.

The housing 10 further provides ribs 10 c in respective sides thereof.The rib 10 c provides a space 10 g through which the screw latch 16passes. The rib 10 c has a function to guide the optical transceiver 1along the rails 3 b prepared in the host system 2, which facilitates theinstallation of the optical transceiver 1 on the host system 2 and theengagement of the electrical plug 19 b with the electrical connector 3 aof the host system. The electrical plug 19 b according to the embodimentprovides electrical pads, the count of which exceeds a hundred and forty(140) within a full width of 72 mm of the optical transceiver 1, then apitch between the electrical pads become less than one millimeter.Accordingly, an alignment mechanism like the rib 10 c and the rail 3 bis preferable or inevitable for the engagement of the electrical plug 19b with the electrical connector 3 a.

FIG. 2 is an exploded view of the optical transceiver 1 shown in FIGS.1A and 1B. FIG. 2 views the optical transceiver 1 from front bottom. Thehousing 10 comprises the upper housing 10 a, which is called as thefirst housing, and the lower housing 10 b, which is called as the secondhousing. A plurality of optical and electrical components is installedwithin a space formed by two housings, 10 a and 10 b. The opticaltransceiver 1 comprises the optical receptacle 14, an opticalmultiplexer 20, an optical demultiplexer 22, a front tray 24, two setsof inner connector 26 and latch unit 28, four (4) ROSAs 30, four (4)TOSAs 32, a circuit board 18, and a plug board 19. Next, respectivecomponents will be roughly described.

FIG. 4A shows the inner structure of the first housing 10 a, and FIG. 4Bshows the inside of the second housing 10 b.

Referring to FIG. 4A, the inside of the first housing 10 a is dividedinto five (5) sections, R₁ to R₅. The first section R₁, which positionsin the front end of the first housing 10 a, mounts the opticalreceptacle 14 and two optical components of the optical multiplexer 20,and the optical demultiplexer 22 in respective sides of the opticalreceptacle 14. The second section R₂ next to the first section R₁ mountsthe front tray 24. The third section R₃ next to the second section R₂mounts the inner connectors 26 and the latch unit 28. The fourth sectionR₄ next to the third section R₃ mounts the circuit board 18 for theelectronic circuit, and the fifth section R₅ mounts the plug board 19for the electronic plug 19 b. The ROSAs 30 and the TOSAs 32 are set inthe rear end of the third section R₃.

In the present optical transceiver 1, only the fourth section R₄installs the electronic components, and the other sections, R₁ to R₃,mount the optical components. The plug board 19 is protected with therear end 10 f of the first housing 10 a as a ceiling. Thus, the opticaltransceiver 1 of the present embodiment clearly distinguishes thesections that mount the optical components from the section thatinstalls the electronic components. Moreover, the optical couplingbetween the OSAs, 30 and 32, and the inner fibers are carried outthrough the inner connector 26 and the latch unit 28 without using anyfiber splicing.

Referring to FIG. 4A, the inside of the first housing 10 a provides aplurality of complex structures. A center of the first section R₁,provides an area 11 a to mount the optical receptacle 14. Both sides ofthe center area 11 a are prepared for mounting the optical multiplexer20 and the optical demultiplexer 22. Two optical components, 20 and 22,are set in respective area by screws.

The second section R₂ is prepared for mounting the front tray 24. Thesecond section R₂ is thicker than the first section R₁ so as to form theterrace 11 b. The terrace 11 b provides a plurality of grooves G₂, andsix grooves G₂ are formed in the present embodiment, within which theinner fibers for connecting the optical receptacle 14 with the opticalmultiplexer 20 and the optical demultiplexer 22, those for connectingthe optical multiplexer 20 with the TOSAs 32, and those for connectingthe optical demultiplexer 22 with the ROSAs 30, are guided and set.

The front tray 24 is fixed on the terrace 11 b with a screw by screwingit in the center hole 11 c. The both sides of the terrace 11 b provide ascrew hole to fix the second housing 10 b to the first housing 10 a.

The inner connectors 24 are mounted in a front end of the third sectionR₃, where a terrace 11 d is formed. This terrace 11 d provides sixgrooves G₄ continuous to the former groves G₂ in the second section R₂.Mounting the front tray 24 and the inner connectors 26 in respectiveregular positions, the inner fibers secured in the grooves G₂ and G₃ arehidden by these components, 24 and 26, which may prevent the innerfibers from straying out from the grooves, G₂ and G₄.

The rear side of the third section G₃ mounts the latch unit 28. Theterrace 11 d in the third section R₃ continues to a terrace 11 e in thethird section R₃. Moreover, the grooves G₄ in the front side of thethird section R₃ also continue to the grooves G₆ of the third sectionR₃. However, the count of the grooves G₆ reduces to four (4) by unifyingouter two grooves into the single groove. The rear end of the thirdsection G₃ provides a plurality of saddles 11 f to mount the OSAs, 30and 32, whose shape corresponds to the outer shape of the stem of theOSAs, 30 and 32. The OSAs, 30 and 32, may be mounted on these saddles 11f so as to put a thermal sheet between the stem and the saddle 11 f, andto set the flange thereof in the latch unit 28. Then, fixing the latchunit 28 to the first housing 10 a by the screws, the OSAs, 30 and 32,are aligned with the first housing 10 a.

The forth section R₄ also provides still another terrace 11 g andgrooves G₈ that are continuous to the former grooves G₆. The innerfibers set in the groves G₈ turn in the forth section R₄ and head torespective target components. Accordingly, the terrace 11 g has a curvedplane shape defining the curvature of the inner fiber. This terrace 11 gprovides a plurality of double terraces in positions facing the IC onthe circuit board 18, for instance, a driver circuit to drive thelight-emitting device in the transmitter unit and a clock and datarecovery circuit in the receiver unit. Theses ICs, as already described,consume large power among components on the circuit board 18. The heatgenerated in these ICs is effectively dissipated to the first housing 10a through the double terraces, 11 g and 11 h. The double terrace 11 hmay come in contact with the ICs directly or indirectly through athermal sheet.

FIG. 4B is a perspective view showing the inside of the second housing11 b and the gasket 34 a attached thereto according to an embodiment ofthe invention. The second housing 11 b includes first to three sections,Q₁ to Q₃, and an area 11 n where the optical receptacle 14 is to bemounted thereon. The first section Q₁ corresponds to the first sectionR₁, the second section Q₂ corresponds to the second and third sections,R₂ and R₃, and the third section Q₃ corresponds to the fourth section R₄of the first housing 10 a.

The gasket 34 a runs in both side ends in the first to third sections,Q₁ to Q₃, in the front end of the first section Q₁, and the rear end ofthe center area 11 n. The second housing 11 b, as shown in FIG. 4B,provides a plurality of bosses 11 m in an inner side of a path alongwhich the gasket 34 a runs. The boss 11 m may temporarily set the gasket34 a during the assembly of the optical transceiver 1. The secondhousing 10 b may provide, instead of the boss 11 m, a tiny wall alongthe inner side of the side wall 11 o. The tiny wall may also prevent thegasket from scattering during the assembly of the optical transceiver 1.

The optical receptacle 14 receives an external optical connector, whichis not illustrated in FIGS. 1 to 4, and optically couples externalfibers in the external connector with the optical devices in the opticaltransceiver 1 to carry out the full-duplex and wavelength divisionmultiplexed optical communication. Referring to FIG. 2, the opticalreceptacle 14 comprises a housing 14 a, a sleeve holder 14 b, aconductive sheet 14 c and two sleeves, 20 c and 22 c. The opticalreceptacle 14 is set in a front center space 11 d formed by twohousings, 10 a and 10 b.

The face panel 12 provides an optical port 12 a in a center thereof. Theface panel 12 is fixed to the front wall 10 d of the first housing 10with screws, which exposed two cavities of the optical receptacle 14 inthe optical port 12 a. The optical receptacle 14 is put between not onlytwo housings, 10 a and 10 b, but between the face panel 12 and the rearwall 11 j in the rear side of the center space 11 a accompanied with thesleeve holder 14 b, the conductive sheet 14, and the sleeves, 20 c and22 c. The receptacle housing 14 a provides two cavities into which thesleeves, 20 c and 22 c and a pair of latch fingers of the sleeve holder14 b protrude. The physical dimensions of the latch finger and thesleeves, 20 c and 22 c, obey the standard of the, what is called as, theSC connector in this embodiment. An inner fiber is extended from the endof the sleeves, 20 c and 22 c, by the pig-tailed arrangement;specifically, the pig-tailed fiber is extracted from the sleeve throughthe U-shaped or the semi-circular cut formed in the rear wall of thespace. The conductive sheet 14 c is put between the rear wall 11 j andthe flange of the sleeve 20 c to eliminate the leakage of theelectro-magnetic radiation from the inside of the optical transceiver 1.

The optical multiplexer 20 and the optical demultiplexer 22 are mountedin respective sides of the optical receptacle 14. The opticalmultiplexer 20 multiplexes four (4) optical signals each having aspecific wavelength different from others and being emitted fromrespective TOSAs 32. While, the optical demultiplexer 22 divides anoptical signal provided from the external fiber into four (4) opticalsignals each having different wavelengths from others and provides theseoptical signals to respective ROSAs 30.

Two inner fibers each extracted from respective sleeves, 20 c and 22 c,enter the optical multiplexer 20 and the optical demultiplexer 22 fromthe rear side thereof after wired in the housing 10. The connection ofthese two inner fibers with the optical multiplexer 20 and the opticaldemultiplexer 22 is also the pit-tailed configuration. As describedlater, the optical transceiver 1 according to the embodiment providesfour inner fibers connecting the optical multiplexer 20 with four TOSAs32, and other four inner fibers connecting the optical demultiplexer 22with four ROSAs 30. Thus, total 8 inner fibers are wired within thehousing 10 as being guided by the front tray 24.

The front tray 24 may guide four inner fibers drawn from the opticalmultiplexer 20 to the TOSAs 32, and other four inner fibers drawn fromthe optical demultiplexer 22 to the ROSAs 30. The optical transceiver 1optically couples plural optical components in the housing 10 thereof.Accordingly, the processing of surplus lengths of the inner fibers is asubject to enhance the productivity of the optical transceiver 1. Thefront tray 24 in the housing 10 may orderly arrange the lengthened innerfibers. Moreover, the first housing 10 a may be made of metaldie-casting and has an enough thickness to form grooves to guide theoptical fiber therein. By arranging the lengthened inner fibers in thegrooves and by the front tray 24, the productivity of the opticaltransceiver 1, in particular, the assembling time may be shortened andthe possibility to cause the damage on the inner fiber may be reduced.

Two sets of inner connectors 26 are provided in the rear side of thefront tray 24. One set of inner connectors 26 is coupled with innerfibers drawn from the optical demultiplexer 22 to the ROSA 30, while theother set of the inner connectors 26 is coupled with the other innerfibers drawn from the optical multiplexer 20 to the TOSA 32. The numberof inner connectors corresponds to the number of the ROSAs 30 and theTOSAs 32, and may be separable so as to mate with respective ROSAs 30and TOSAs 32. The inner connectors 26 may be individually operable.

As described later in the specification, surplus lengths of the innerfibers are set in the front tray 24 and in the grooves formed in thehousing 10 during the assembly of the optical transceiver 1, and theinner connectors 26 are temporarily mated with fingers of the front tray24. Setting the ROSAs 30 and the TOSAs 32 accompanied with latch unit 28on the housing 10 a, the latch unit 28 faces the inner connectors 26.Then, sliding the inner connectors 26 rearward to latch the innerconnectors 26 with respective latch units 28, the inner fibers drawnfrom the optical multiplexer 20 may couple with the TOSAs 32, and theother inner fiber drawn from the optical demultiplexer 22 may couplewith the ROSAs 30. Thus, the optical coupling between the OSAs, 30 and32, and the external fiber may be realized through the couplingmechanism of the inner connectors 26 and the latch unit 28. Accordingly,even when only one of OSAs, 30 and 32, causes a failure, this troubledOSA may be easily and promptly replaced only by releasing only one ofthe inner connectors 26 corresponding to the troubled opticalsubassembly from the latch unit 28.

The optical transceiver 1 of the embodiment installs the circuit board18 and the plug board 19 in the rear of the OSAs, 30 and 32. The circuitboard 18 installs a plurality of electrical components in both surfacesthereof, while, the plug board 18 b installs the electrical plug 19 b inthe rear end thereof.

Electronic components include several ICs that show the large heatdissipation, for instance, a driver for an LD in the transmitter unitand a clock and data recovery in the receiver unit. To secure the heatconducting path from such ICs, the first housing 10 a provides severalterraces in the inner surface thereof to come in thermally contact withsuch ICs. The housings, 10 a and 10 b, provide a thick metal case formedby the die-casting, which shows large heat capacity, and the thick casemakes it possible to form the mesa. Moreover, a depression between themesas may show a function to guide the inner fibers therein.

The plug board 19 provided in the rear of the circuit board 18 mountsthe electronic plug 19 b. The present optical transceiver 1 may show theoptical transmission speed of 40 Gbps or 100 Gbps by communicating withthe host system in four (4) channels for the transmitter unit and otherfour (4) channels for the receiver unit. Then, each channel is necessaryto transmit an electrical signal with the speed of 10 Gbps or 25 Gbps.Such an electrical signal with high speed is ordinarily handled inaccordance with the LVDS (Low Voltage Differential Signal) standard.That is, each signal channel is necessary to have a pair of signal pins;then, total 16 pins are necessary to transmit electrical signals.Moreover, the transmission of the high speed signal is inevitable toreinforce the ground (GND) line. A pair of GND lines ordinarily sets thesignal line therebetween to secure the signal quality. Still further,because the optical transceiver 1 installs 4 channels for thetransmission and other 4 channels for the reception, the powerconsumption of the whole circuit becomes quite large and a plurality ofpower pins becomes necessary.

Accordingly, the present optical transceiver 1 provides the electronicplug 19 b with over 140 pins within the full width of 72 mm, whichinevitably reduces the pin pitch of the plug 19 b to a distance lessthan 1 mm and requests the high dimensional accuracy to the circuitboard 18. When such an electrical plug with the high dimensionalaccuracy is prepared in a large board, the circuit board 18 becomes costineffective. The present optical transceiver 1 divides the circuit boardinto two parts, one of which 18 has a large area and mounts theelectronics circuit and the other 19 provides the electronic plug 19 bin relatively smaller area.

Next, respective optical and electrical components installed in theoptical transceiver 1 will be further described with modificationsthereof.

Referring to FIGS. 2, 4A and 4B again, the optical transceiver 1 of thepresent embodiment may provide two gaskets, 34 a and 34 b, which have arod shape and made of elastic member, typically, rubber tube with metalcoating.

The gasket 34 a runs, in the section Q₁ corresponding to the firstsection R₁, on the side wall and the walls defining the area 11 n tomount the optical receptacle 14 therein as illustrated in FIG. 4B. Inthe section Q₂ corresponding to the second and third sections, R₂ andR₃, the gasket 34 a runs on the side wall of the second housing 10 b. Inthe section Q₃ corresponding to the forth section R₄, the gasket 34 a isset in the groove 10 o provided in the top of the side walls and runsalong the ground pattern on the circuit board 18. The other gasket 34 bis set in the groove 10 h of the first housing 10 a and runs along theother ground pattern provided in the back surface of the circuit board18.

Assembling the first housing 10 a with the second housing 10 b, thefirst gasket 34 a is put between the housings, 10 a and 10 b, in thefirst to third sections, R₁ to R₃; while in the fourth section R₄, thegasket 34 a is put between the second housing 10 b and the groundpattern on the surface of the circuit board 18, and the other gasket 34b is put between the first housing 10 a and the other ground pattern inthe back surface of the circuit board 18. This arrangement of the twogaskets, 34 a and 34 b, and the housings, 10 a and 10 b, mayelectrically shield the circuit on the circuit board 18 from not onlythe outside of the optical transceiver 1 but the area 11 a where theoptical receptacle 14 is mounted.

FIGS. 5A and 5B magnify the front portion of the optical transceiver,where, FIG. 5A is a plan view and FIG. 5B is a cross section thereof.When the second housing 10 b is assembled with the first housing 10 a,the gasket 34 a is held between two housings, 10 a and 10 b. Referringto FIG. 5A, the gasket 34 a may run on the side walls 11 i and the rearwall 11 j of the first housing 10 a so as to surround the center area 11a. Moreover, as shown in FIG. 5B, the gasket 34 a may come in contactwith the conductive sheet 14 c put between the optical receptacle 14 andthe rear wall 11 j, which may securely shield the space 11 a.

The circuit board 18 will be further described. FIG. 7A is a perspectiveview showing the circuit board 18 and the plug board 19, FIG. 7B showsthe circuit board 18 without any components thereon, FIG. 7C shows across section of a side edge portion of the circuit board, and FIG. 7Dshows the plug board 19. The optical transceiver 1 according to thepresent embodiment, as already describe, divides boards for theelectronic components into two parts, one of which is the circuit board18 and the other is the plug board. Two boards, 18 and 19, are coupledwith edge connector.

The circuit board 18 mounts a plurality of electrical components. TheROSAs 30 are connected to the circuit board 18 in one surface thereofthrough respective FPC (flexible printed circuit board 18 d; while, theTOSAs 32 are connected to the circuit board 18 in the other surface alsothrough respective FPC boards 18 d. This arrangement to distinguish thereceiver unit from the transmitter unit by the surfaces thereof mayreduce the electrical crosstalk between both units. The clock and datarecovery ICs 18 r are arranged in a side close to the ROSA 30 of thefront surface of the circuit board 18, while, the driver ICs, which arenot illustrated in FIG. 6A, are arranged in the side close to the TOSAs32 but in the back surface. The arrangement of the CDR ICs 18 r and thatof the driver ICs make it possible for the optical transceiver 1 of thepresent embodiment to follow the transmission speed of 40 Gbps or 100Gbps.

FIG. 6A is a perspective view showing a first housing 110 a according toanother embodiment of the present invention, and FIG. 6B is aperspective view of the first housing 110 a where whole opticalcomponents are installed therein. As illustrated in FIG. 6A, the firsthousing 110 a omits the groove G₈ in the fourth section R₄; instead, thefourth section R₄ provides two terraces 111 g. One of the terraces 111 gis formed neighbor to the saddle 111 f in the transmitter side, whilethe other 111 g is formed in center of the section R₄ in the receiverside. These two terraces 111 g provide an area for arranging the thermalsheet 18 t, whose positions correspond to the position of the driver ICmounted on the circuit board 18. The terrace 111 g forms the doubleterrace 111 h to which the CDR IC mounted on the first board 18 comes incontact.

Other areas in the fourth section surrounding the terrace 111 g, areformed in flat on which the rear tray 136 is mounted. The rear tray 136may guide the inner fibers, F₂ to F₈, in the fourth section R₄. The reartray 136 comprises a primary plate 136 a, a fastened portion 136 b, anda plurality of eaves 136 c. The primary plate 136 a has a shapesubstantially identical with the opened area in the fourth section R₄.The fastened portion 136 b provides a hole aligned with the tapped holein the terrace 111 g. The rear tray 136 may be fixed to the firsthousing 110 a by the screws. The eaves 136 c may control the innerfibers, F₂ to F₈. Specifically, the eaves 136 c each rise from the outerand inner edges of the primarily plate 136 a and are bent inward. Theinner fibers, F₂ to F₈, may be covered by the bent portion of the eaves136 c; thus, the inner fibers, F₂ to F₈, may be prevented from strayingout. The surface of the eaves 136 c may come in contact, directly orindirectly through a heat spreader, with the circuit board 18 to secureanother heat conducting path from the circuit board 18 to the firsthousing 110 a.

As shown in FIG. 7B, the circuit board 18 provides an edge connector 18p in one end thereof, where a plurality of electrical pads are includedin the edge connector 18 p. The circuit board 18 also provides edgeportions 18 f and a pair of ground patterns 18 e along the respectiveedges 18 f thereof. Although not shown in FIG. 7B, the back surface ofthe circuit board 18 also provides the ground pattern 18 e in a positioncorresponding to the ground pattern 18 e on the front surface 18 a, andthese ground patterns 18 e are connected with through holes 18 v asshown in FIG. 7C. The ground pattern 18 e in the front surface 18 a ofthe circuit board 18 electrically comes in contact with the secondhousing 10 b through the gasket 34 a, while, the ground pattern 18 e inthe back surface comes in contact with the first housing 10 a throughthe gasket 34 b. Thus, the electronic components mounted on the circuitboard 18 are surrounded by the frame ground.

FIG. 8A is a horizontal cross section of the optical transceiver 1,while, FIG. 8B magnifies an edge portion of the optical transceiver 1.

The edges 18 f of the circuit board 18 are put between the first andsecond housings, 10 a and 10 b, through respective gaskets, 34 a and 34b. Because the gasket, 34 a and 34 b, is made of elastic member, thecircuit board 18 may be elastically supported by the housings, 10 a and10 b, which may reduce the stress caused in the connection between thecircuit board 18 and the plug board 19, namely, in the solderedconnection between the pads of the edge connector 18 p and the socketpins 19 g.

Because the gasket, 34 a and 34 b, may be made of electricallyconductive material and come in contact with the ground patterns 18 e ofthe circuit board 18, which enables the frame ground, namely the chassisground, to be conducted on the circuit board 18.

FIG. 8C is a cross section showing a modified embodiment of the presentinvention, where FIG. 8C also magnifies the edge portion 18 f of thecircuit board 18. The embodiment shown in FIG. 8C provides the groundpattern 18 w formed so as to envelope the edge 18 f of the circuit board18. When the circuit on the circuit board 18 is necessary to be mountedin high density, the circuit board 18 sometimes becomes hard to providea plurality of ground vias connecting the front and back surfacesthereof. In such a case, the ground pattern 18 w enveloping the edge ofthe circuit board 18 may provide the chassis ground by coming in contactwith the first and second housings, 10 a and 10 b, through theconductive gaskets, 34 a and 34 b.

FIG. 9A shows a modified embodiment of the gasket 134 according to thepresent invention, while FIG. 9B magnifies the cross section of the edgeportion of the circuit board 18 implemented with the modified gasket 134shown in FIG. 9A. The gasket 134 has the U-shape with the slab portion134 a and two legs 134 b and 134 c. The U-shaped cross section of thegasket 134 may envelope the edge portion 18 f of the circuit board 18.Moreover, the legs each has a plurality of fins, 134 d and 134 e, wherethey come in elastically contact with the first and second housings, 10a and 10 b. The gasket 134 shown in FIGS. 9A and 9B, may show thefunction same as those shown by the gasket 34.

Referring to FIG. 7D, the plug board 19 provides a socket portion 19 cand a plug portion 19 f. The socket portion 19 c includes a plurality ofpins 19 g and receives the edge connector 18 p of the circuit board 18.The pins 19 g may be soldered to the pads of the edge connector 18 p andelectrically connected to respective plug pads 19 b within the plugportion 19 f. Accordingly, mating the pads 19 b of the plug portion 19 fwith the connector 3 a on the host system 2, the circuit on the circuitboard 18 may be electrically coupled with the host system 2.

The plug board 19 may further include a projection 19 d and a rib 19 e.The projection 19 d is formed in the side of the plug portion 18 f,while, the rib 19 e is formed in both surfaces of the socket portion 19c. Referring to FIG. 2 again, the optical transceiver 1 may provide ametal cover 35, which may be made of metal plate and has a shapeenveloping the rib 19 e, and a groove 10 v in the first housing 10 a.The groove 10 v of the housing 10 a receives the rib 19 e accompaniedwith the metal cover 35. Similarly, the second housing 10 b may providethe other groove 11 v to receive the rib 19 e in the back surface of theplug board 19 accompanied with another metal cover 35. The metal cover35 may elastically come in contact with the housings, 10 a and 10 b.

In the arrangement around the plug board 19, the projection 19 d mayabut against the rear wall 10 e of the first housing 10 a to positionthe circuit and plug boards, 18 and 19, when the optical transceiver 1mates with the electrical connector 3 a of the host system 2. Moreover,because the rib 19 e on the plug board 19 is set within the grooves, 10v and 11 v, the plug board 19 may be prevented from making backlash whenthe plug 19 b is extracted from the host connector 3 a. The arrangementof the rib 19 e and the projection 19 d may protect the plug board 19from the mechanical stress.

Details of the metal cover 35 and the mechanism to be assembled with theplug board 19 will be further described. FIG. 10A shows a metal cover 35according to an embodiment of the invention. The metal cover 35 has theU-shaped cross section so as to trace the cross section of the rib 19 ein the plug board 19. Specifically, the metal cover 35 includes a slabportion 35 a, a plurality of primary legs 35 b with an extended widthand secondary legs 35 d with a narrower width but extending outwardlycompared to the primary legs 35 b. The primary legs 35 b are bent inboth edges of the slab portion 35 a; while, the secondary legs 35 d arebent in only one edge of the slab portion 35 a. Two legs, 35 b and 35 d,are alternately arranged with each other. The metal cover 35 furtherprovides a plurality of fins 35 c in the slab portion 35 a.

As shown in FIGS. 4A and 4B, the rear end of the first and secondhousings, 10 a and 10 b, provides the groove, 10 v and 11 v,respectively, into which the metal cover 35 is set. FIG. 10C is a crosssection showing the rib 19 e, the metal cover 35, and the grooves, 10 vand 11 v. The ribs 19 e in both surfaces of the plug board 19 may becovered by the metal cover 35 by the U-shaped cross section thereof, andthe metal cover 35 is set within the grooves, 10 v and 11 v, inrespective housings, 10 a and 10 b. The secondary legs 35 d and the fins35 c come in contact to the rear and bottom walls of the grooves, 10 vand 11 v.

FIG. 10B shows a metal cover 135 according to another embodiment of theinvention. The metal cover 135 of the present embodiment also has theU-shaped cross section fit to the shape of the rib 19 b. The metal plate135 of the present embodiment further provides a tab 135 e in additionto the primary and secondary legs, 135 b and 135 d. The tab 135 eextends toward a direction opposite to a direction to which thesecondary legs 135 d extends. The tab 135 e of the present embodimentmakes the direction of the metal cover easily distinguishable.

In a further modified embodiment, the groove, 10 v and 11 v, may havetwo types of depths alternately arranged to others. The deeper portionmay receive the fin 35 c, that is, the tip of the fin 35 c of the metalcover 35 comes not in contact with the bottom of the groove, 10 v and 11v. In this embodiment, the metal cover 35 is not affected by the elasticforce along the depth direction of the groove, 10 v and 11 v.

The secondary leg 35 d and the rib 19 e may securely prevent the metalcover 35 from sliding within the groove, 10 v and 11 v, which protectsthe edge connector 18 p and the socket pins 19 g from breakage even whenthe optical transceiver 1 is set on the host system 2, or removed fromthe host system 2. On the other hand, the circuit board 18 iselastically supported by the first and second housing, 10 a and 10 b.

Next, the optical multiplexer 20 and the optical demultiplexer 22 willbe described accompanied with the inner fibers, F₂ to F₈, extendingtherefrom. Although FIG. 11A shows a perspective view of the opticalmultiplexer 20 with the inner fibers, F₂ and F₆, the same arrangementwith those shown in FIG. 11A are applicable to the optical demultiplexer22 and the inner fibers, F₄ and F₈.

In the rear end of the optical multiplexer 20, two inner fibers F₆heading to the TOSAs 32 are output from one side, while, the other sidethereof outputs three inner fibers, F₆ and F₂. These inner fibers, F₂and F₆, have the pig-tailed configuration. During the assembly of theoptical transceiver 1, the optical multiplexer 20 with five innerfibers, F₂ and F₆, is mounted on the first housing 10 a. Respectivelengths of the inner fibers, F₂ and F₆, are pre-adjusted in advance tothe installation because the positions of the optical components arepredetermined and the lengths of the fibers connecting them are alsodetermined. The optical transceiver 1 of the present embodiment installsthe inner connectors to couple the inner fibers F₆ with the TOSAs 32without using any fusion splicing of the fibers. Fusion splicing isgenerally necessary to prepare a surplus length of fibers, and thissurplus length of fibers is necessary to be orderly enclosed within thehousing. The present optical transceiver, as described above, uses theinner connectors 26 without preparing any surplus length of the innerfibers, F₂ and F₆.

As shown in FIG. 11B, the sleeve assembly may be made of metal andincludes, from the front thereof, the first cylinder 20 c, the flange 20e and second cylinder 20 f. The second cylinder receives the innerfiber, F₂ and F₄, coming from the optical multiplexer 20, or the opticaldemultiplexer 22. The sleeve assembly may couple the external fiberinserted into the first cylinder with the inner fiber, F₂ and F₄,secured in the second cylinder 20 f, then, the external fiber mayoptically couple with the TOSAs 32.

Next, the front tray 24, the inner connectors 26 and the latch unit 28installed in the optical transceiver 1 according to the presentembodiment will be further described.

FIG. 12 is a perspective view showing the front tray 24 of an embodimentof the present invention. The tray 24, as already described, providesfour (4) slots 24 a for guiding the inner fibers F₆ coupled with theoptical multiplexer 20 with the TOSAs 32 and other four (4) slots 24 afor guiding the inner fibers F₈ connecting the optical demultiplexer 22with the ROSAs 30. The slots 24 a have the same pitch in the rear sidethereof. The pitch is substantially equal to the arrangement of theOSAs, 30 and 32; but the slots 24 a are gradually bent toward the centeras closing the optical receptacle 14.

Respective slots 24 a accompany with a pair of latch fingers 24 b in therear end thereof. The latch fingers 24 b may engage with the innerconnector 26. The slot 24 a gradually narrows the width thereof from therear to the front and has a stopper 24 c and an eave 24 d in a frontside thereof to prevent the fibers, F₆ and F₈, set within respectiveslots 24 a from straying out. One side portion of the front tray 24provides a guiding space 24 e, into which the inner fibers F₈ heading tothe fourth region R₄ pass, and a wall 24 g for setting a curvature ofthe inner fibers F₈, while, the other side portion provides anotherguide space 24 f and a wall 24 h, through which the inner fibers F₆heading to the fourth region R₄ pass and the wall 24 h determines thecurvature of the fibers F₆. This front tray 24 may be fixed to the firsthousing 10 a with a screw passing through the center hole 24 r andengaged with the tapped hole 11 c shown in FIG. 4A.

FIG. 13A is a perspective view showing a front tray 124 according toanother embodiment of the invention, while FIG. 13B is a plan viewshowing the front tray 124 that sets the inner fibers, F₆ and F₈, inrespective slots.

The front tray 124 includes a front portion 124A and a rear portion124B. The rear portion provides a plurality of slots 124 a with a pairof latch fingers 124 b and a eave 124 d to prevent the inner fiber fromstraying out and a tapped hole 124 r. The rear portion 124B furtherprovides, in respective sides thereof, a ceiling 124 s and guide walls,124 t and 124 u, where they constitute a guide slot 124 w for the innerfibers, F₆ and F₈, which are drawn longitudinally along the edge of thefirst housing 10 a to head to the lateral direction.

The front portion 124A may guide the inner fibers, F₆ and F₈, andprovides a front wall 124 v and front eaves 124 x. The front wall 124 vextends laterally to prevent the inner fibers, F₆ and F₈, fromprotruding forwardly; while, the front eaves 124 x extend backward fromthe front wall 124 v so as to cover the front portion of the tray 124.The structures, 124 v and 124 x, may prevent the inner fibers, F₆ andF₈, from straying out from the front portion 124A. The inner fibers, F₆and F₈, which are drawn along the side of the front tray 124 and benttoward lateral direction, may be covered by the ceiling 124 s at theside and the front eaves 124 x.

FIG. 14 illustrates an intermediate assembly of the inner connectors 26,the latch unit 28 and OSAs 30. Next, details of the inner connector 26will be described. The inner connector 26, as shown in FIGS. 15A and15B, provides two spaces, 26 a and 26 b, in the rear and front sidethereof, respectively. These two spaces, 26 a and 26 b, are partitionedby the center wall 26 c. The rear space 26 a receives the coil member 20a attached in the end of the inner fibers F₆ shown in FIG. 11A. The rearspace 26 a also provides an opening 26 d in respective side fingers 26 sthereof, which are engaged with the projection 28 c of the latch unit28. The side fingers 26 s has a U-shaped cross section, where the latchfinger 28 b of the latch unit, which is described later in detail, is tobe set within the U-shape. Engaging the projection 28 c with the opening26 d, the inner connector 26 may engage with the latch unit 28.Concurrently with this engagement, the ferrule 20 b in the tip of theinner fibers F₆ may be inserted within the bore of the sleeve 30 d ofthe ROSA 30, which may optically couple the inner fiber F₆ with thesemiconductor optical device in the ROSA 30.

The coil member 20 a, which is set in the rear space 26 a, abuts againstthe center wall 26 c to push the ferrule 20 b toward the ROSA 30 whenthe inner connector 26 is engaged with the latch unit 28, which makesthe physical contact between the tip of the ferrule 20 a and the tip ofthe stub secured within the sleeve 30 d. Thus, the optical transceiver 1of the present embodiment may realize the optical coupling between theinner fiber F₆ and the ROSA 30 by the physical contact (PC) arrangementwithout using any fusion splicing between fibers. Accordingly, even whenone of the OSAs, 30 and 32, causes failure, only the degraded OSA may beeasily replaced without influencing the rest OSAs.

The front side wall of the inner connector 26 provides a groove 26 ewithin which two projections 26 f and 26 g are formed. The groove 26 ereceives the latch finger 24 b of the front tray 24. The inner connector26 may slide in front and rear along the latch finger 24 b. When theprojection provided in the edge of the latch finger 24 b engages withthe first projection 26 g provided in the deeper side of the groove 26e, that is, the projection of the latch finger 24 b is set in the pocketformed between the deeper side projection 26 g and the end wall of thegroove 26 e, the inner connector 26 temporarily positions apart from thelatch unit 28 by being pulled in the side of the front tray 24. When theoptical coupling between the inner fiber F₆ with the OSA, 30 or 32, isfinally performed, the projection of the latch finger 24 b slides withinthe groove 26 e and engages with the second projection 26 f.

FIGS. 16A to 16D describe an inner connector 126 and the stopper 127combined with the inner connector 126 according to another embodiment ofthe present invention, where FIG. 16A is an exploded view, FIG. 16Bshows an assembled connector, FIG. 16C is a perspective view of theinner connector, and FIG. 16D is a cross section showing the positionalrelation between the inner connector, the stopper, the inner fiber, andthe latch finger 24 b of the front tray 24.

The ferrule 20 b provided in the tip of the inner fiber, F₆ and F₈,accompanies with a flange 20 d. The coil member 20 a, which continuesfrom the ferrule 20 b, is put between the center partition 126 c of theinner connector 126 and this flange 20 d. The inner connector 126,similar to those 26 shown in FIGS. 15A and 15B, provides two spaces, 126a and 126 b, the former of which is put between two side fingers 126 sand bottom wall, while, the latter of which is formed by another housingportion 1261. The stopper 127, which is made of metal plate, includes abeam 127 a and a pair of legs 127 b each extending from the beam 127 a;thus, the stopper 127 has the U-shaped cross section. The beam 127 aprovides an opening 127 d, through which the ferrule 20 b passes whosediameter is less than a diameter of the flange 20 d. The end of the leg127 b provides a tab 127 c that engages with a hook 126 q formed in thetop of the center wall 126 c of the inner connector 126.

The inner fiber, F₆ and F₈, is set in the inner connector 126 such thatthe ferrule 20 b passes the opening 127 d in the beam 127 a of thestopper 127 as the inner fiber, F₆ and F₈, is set within the front space126 b, and the stopper 127 engages with the inner connector 126 suchthat the tab 127 c engages with the hook 126 q as abutting the coilmember 20 a against the center partition 126 c. Because the diameter ofthe flange 20 d is larger than that of the opening 127 d, the rearwardmotion of the ferrule 20 b may be prevented by the stopper 127.Accordingly, the inner fiber, F₆ and F₈, and the ferrule 20 d may beprevented from disassembled with the inner connector 126.

The inner connector 126 of the present embodiment further provides thegroove 126 e in the side of the housing 1261. The groove 126 e includestwo pockets, 126 m and 126 n, and three projections, 126 f to 126 h. Thefirst pocket 126 m is put between the first and third projections, 126 fand 126 h, while, the second pocket 126 n is formed in a deeper side ofthe second projection 126 g. Two pockets, 126 m and 126 n, may receiveand engage with the hook in the tip of the latch finger 124 b of thefront tray 124.

As illustrated in FIG. 16D, sliding the inner connector 126 rearward toset the tip of the latch finger 124 b in the first pocket 126 m, the tipof the ferrule 20 b moves in the position where the ferrule 20 boptically couples with the OSA, 30 and 32. On the other hand, slidingthe inner connector 126 frontward to set the tip of the latch finger 124b in the second pocket 126 n, the ferrule 20 d may not interfere withthe latch unit 128 and the OSA, 30 and 32.

Accordingly, sliding the inner connector 126 rearward to engage thelatch finger 124 b with the first projection 126 g at the first pocket126 m in advance to set the latch unit 128 and the OSA, 30 and 32, inrespective position in the housing 10 a, the ferrule 20 b may be set inthe regular position without engaging with the latch unit 28. Then, theinner fiber, F₆ and F₈, may be drawn within the first housing 10 a asthey are set in the final position. After drawing the inner fiber, F₆and F₈, fixing them thereat, and sliding the inner connector 126frontward to engage the latch finger 124 b with the second projection126 g at the second pocket 126 n, the latch unit 28 and the OSA, 30 and32, may be assembled within the first housing 10 a without beinginterfered with the ferrule 20 b and the inner connector 126.

FIG. 17 is a perspective view showing another type of the innerconnector 226 which is modified from that shown in FIG. 16B. Themodified inner connector 226 shown in FIG. 17 provides the groove 226 ewith two pockets, 226 m and 226 n, but provides only one projection 226f. Other projections, 126 g and 126 h, appeared in the former embodimentare replaced by a terrace connecting these two projections. This type ofthe inner connector 226 may show the same function as those appeared inthe former embodiment 126; that is, two pockets, 226 m and 226 n,determines two position of the ferrule 20 b.

As illustrated in FIGS. 14 and 18, where FIG. 18A is viewed from thebottom; while, FIG. 18B is viewed from the top thereof, the latch unit28 provides four slots 28 a corresponding to the number of the ROSAs 30.Each slot 28 a accompanies with a pair of latch fingers 28 b inrespective sides thereof, and the latch finger 28 b provides aprojection 28 c in the outer surface. This projection 28 c engages withthe opening 26 d of the inner connector 26 to mate the inner connector26 with the latch unit 28. The rear side of the latch unit 28 provides aslit 28 e.

FIG. 19A is a side view of the ROSA 30, while, FIG. 19B shows one slotof the latch unit 28 viewed from the rear. The ROSA 30, as shown in FIG.19A, has two flanges, 30 a and 30 b along the optical axis thereof, anda neck 30 c between the flanges, 30 a and 30 b. While, the latch unit 28provides a horseshoe-shaped cut 28 g in the rear wall 28 h thereof, asillustrated in FIG. 19B. The diameter L₂ of the neck 30 c of the ROSA 30is set to be slightly larger than the frontage L₁ of the cut 28 g.Because the latch unit 28 is made of resin, the ROSA 30 may be easilyset in the latch unit 28 as expanding the frontage of the cut 28 g. TheROSA 30, once set in the latch unit 28, becomes hard to be dropped fromthe cut 28 g, which may enhance the productivity of the intermediateassembly. As illustrated in FIG. 14, the front flange 30 a of the ROSA30 is set in the slit 28 e of the latch unit 28, and the sleeve 30 d isset within one of the slot 28 corresponding thereto. In FIG. 19A, theOSA, 30 and 32, comprises a sleeve member 30 s that includes, asdescribed above, the sleeve 30 d, the front flange 30 a, a neck 30 c,and the rear flange 30 b; and an optical device 30 e. The sleeve member30 s may optically couple the inner fiber, F₆ and F₈, with the opticaldevice 30 e; while, the optical device 30 e installs a semiconductoroptical device, such as a photodiode for the ROSA 30 and a laser diode(LD) for the TOSA 32.

The latch unit 128 according to another embodiment of the opticaltransceiver 1 will be described as referring to FIG. 18B. The latch unit128 of the present embodiment includes, in addition to structures shownin FIG. 18A, a projection 128 k in a side wall thereof. This projectionmay prevent the inner fibers passing thereunder from straying out.

FIG. 20 is a cross section taken along the optical axis of the innerfiber, F₆ or F₈, set in the inner connector 126. Mating the innerconnector 126 with the latch unit 128, the ferrule 20 b of the innerfiber F₆ is inserted within a bore of the sleeve assembly 30 s and thetip thereof comes in physically contact with a tip of the stub 30 u ofthe OSA 30 set in the latch unit 128. The coil member 20 a comes in oneend thereof in contact with the center partition 126 c of the innerconnector 126 and the other end comes in contact with the flange 20 d,which pushes the ferrule 20 b toward the OSA 30. Then the physicalcontact between the tip of the ferrule 20 b and that of the stub 30 umay be securely realized even in a limited inner space of the opticaltransceiver 1.

Another modification of the inner connector, 26 and 126, has anarrangement of the groove, that is, the first embodiment of the innerconnector 26 provides two projections, 26 f and 26 g, while, the secondembodiment provides three projections, 126 f to 126 h, or one projection126 f with the terrace connecting rest two projections, 126 g and 126 h.The still modified inner connector may provide only one projection inthe groove 126 e. The one projection merely hooks the latch finger, 24 band 124 b, to prevent the inner connector 26 and 126, from slipping outfrom the front tray 24 during the assembly of the optical transceiver 1.Coupling the inner connector with the latch unit 28, the inner connectormay be free from the front tray 24. When only a limited space is leftbetween the front tray 24 and the latch unit 28, the arrangement of theinner connector thus described becomes effective.

Another type of the housing 110 and the optical receptacle mounted inthe front center of the housing will be described. FIG. 21A is aperspective view showing a front portion of the first housing 110 aaccordingly to another embodiment of the present invention, and FIG. 21Bis a front view thereof. As shown in FIGS. 21A and 21B, the frontportion of the first housing 110 a includes a center area 111 apartitioned by side walls 111 i and the rear wall 111 j. The rear wall111 j provides a pair of double cuts each including a base cut S₁ andsub cut S₂. The pitch between the base cuts S₁ is identical with thepitch between the sleeves of the SC type optical connector, while, thepitch between the sub cuts S₂ is narrower than the pitch of the basecuts S₁ and identical with the pitch of the LC type optical connector.

The first housing 110 a includes two types of grooves, G₂S and G₂L, inthe second section R₂. The distance between the outer grooves G₂S issubstantially identical with the pitch of the base cut S₁, while, thedistance between the inner grooves G₂L is equal to that of the sub cutS₂. The first housing 110 a further provides the grooves, G₄S and G₄L,in the third section R₃ and they continue from the correspondinggrooves, G₂S and G₂L, in the second section R₂. Thus, these grooves G₂Sto G₄L are arranged in straight.

FIGS. 22A to 22C illustrate an optical receptacle with the type of theSC receptacle according to a modification of the present invention,where the optical receptacle 114 is assembled in the center area 111 a.FIG. 22A views the optical receptacle 114 from the rear, FIG. 22B viewsthe optical receptacle 114 from the front, and FIG. 22C is an explodedview of the optical receptacle 114. Similar to the optical receptacle 14shown in FIG. 2, the modified optical receptacle 114 includes thehousing 114 a, the sleeve holder 114 b, and the conductive sheet 114 c.

The optical receptacle 114 includes two cavities, 114A and 114B, toreceive the first cylinder, 20 c and 22 c, of the sleeve assembly. Twocavities, 114A and 114B, are partitioned by the rear wall 114 e to whichthe front surface of the flange 20 e comes in contact. The rear wall 114e also provides two openings 114 h through which the first cylinder 20 cpasses. Each opening 114 h accompanies with a step 114 k in a peripherythereof into which the flange, 20 e and 22 e, of the sleeve assembly isset.

The conductive sheet 114 c is attached to the rear wall 114 e. Theconductive sheet 114 c, which is made of electrically conductivematerial, for instance, it may be made of electrically conductivenon-woven fabric. The optical receptacle 114 thus assembled the housing114 a with the sleeve assemblies, 20 and 22, and the conductive sheet114 c is installed on the center area 111 a of the first housing 110 aas shown in FIG. 23.

Specifically, the second cylinders, 20 f and 22 f, of the sleeve memberare set on respective base cuts S₁ as passing the rear wall 111 j of thecenter area 111 a. The optical receptacle shown in FIGS. 22 and 23 hasthe configuration of the SC type receptacle. The conductive sheet 114 cis put between the rear wall 114 e of the receptacle housing 114 a andthe rear wall 111 j of the center area 111 a. Screwing the face cover 12to the front wall 110 d of the first housing 110 a, the face cover 12presses the optical receptacle 114 against the rear wall 111 j, then,the conductive sheet 114 c may be securely set between the opticalreceptacle 114 and the rear wall 114 j.

The optical receptacle 114 according to the present embodiment mayfurther provide a lug 114 f secured in the side wall 114 g only by anend portion thereof. The lug 114 f extends up and down from the securedportion. Accordingly, the lug 114 f in the other end thereof may betwisted around the secured portion. The first housing 110, on the otherhand, provides a pocket 111 k in both side walls 111 i of the centerarea 111 a. When the optical receptacle 114 is set on the center area111 a, the front surface of the lug 114 f abuts against the rear surfaceof the pocket 111 k, which presses the optical receptacle 114 rearwardagainst the rear wall 111 j and may temporarily fix the opticalreceptacle 114 until it is finally sandwiched between the face cover 12and the rear wall 111).

Further specifically describing the relation between the face cover 12and the optical receptacle 114, the face cover 12 as shown in FIG. 24provides a port 12 a through which the optical receptacle 114 isexposed, and two pairs of holes, 12 b and 12 c, the former of which 12 cpasses the screw latch 16 therethrough, while the latter 12 b passes thescrew for fixing the face cover 12 to the first housing 110 a. The port12 a provides in both sides thereof a pressing tab 12 d extendingrearward. The pressing tab 12 d abuts the optical receptacle 114 againstthe front wall 114 j of the optical receptacle 114. Pressed by the facecover 12, the optical receptacle 114 is pushed rearward, and the rearsurface of the flange of the sleeve assembly, 20 e and 22 e, comes incontact with the rear wall 111) as putting the conductive sheet 114 ctherebetween.

As shown in FIG. 22C, the conductive sheet 114 c provides holes 114 r,through which the first cylinder, 20 c and 22 c, of the sleeve assemblypasses. In the present embodiment, the hole 114 r has diameter slightlyless than a diameter of the first cylinder, 20 c and 22 c, then, thefirst cylinder, 20 c and 22 c, is inserted into the hole 114 r and theopening 114 h as expanding the size of the hole 114 r, which may preventto cause a gap between the first cylinder, 20 c and 22 c, and the hole114 r and securely shield the inside of the housing 110.

Still further, the rear wall 114 e of the receptacle housing 114 aprovides a plurality of protrusions around the step 114 k which may makethe conductive sheet 114 c reliably contact to the rear wall 111 j.

FIG. 25 shows another embodiment of the optical receptacle 214 accordingto the present invention. The optical transceiver 1 of the presentinvention may install the optical receptacle 214 with the LC typeconfiguration instead of the SC type receptacle shown in FIGS. 22 a to23. The pitch between two sleeves of the LC type receptacle is narrowerthan that of the SC type receptacle. Accordingly, the opticaltransceiver 1 of the present embodiment provides the double cut; thebase cut S₁ and the sub cut S₂, in the rear wall 111 j of the firsthousing 110 a; where the former cut S₁ is for the SC type opticalreceptacle and the latter cut S₂ is for the LC type connector. Moreover,the second section R₂ provides two types of guiding grooves, G₂S andG₂L, as shown in FIGS. 21A and 21B. Two grooves G₂S are prepared for theinner fibers, F₂ and F₄, drawn from the sleeve assembly of the SC typereceptacle 114; while, the grooves G₂L are prepared for the innerfibers, F₂ and F₄, output from the LC type receptacle 214. Thus, theoptical transceiver 1 according to the present embodiment may beapplicable to two types of the optical receptacles, namely, the SC typereceptacle and the LC type receptacle.

FIGS. 26A and 26B illustrate still another embodiment of the opticalreceptacle 314 applicable to the optical transceiver 1. The receptaclehousing 314 a shown in FIGS. 26A and 26B has features in the lug 314 fand protrusions 314 n distinguishable from the former embodiments.

The lug 314 f in the present embodiment has a crushable rib when the lug314 is set within the pocket 111 k of the first housing 110 a.Specifically, the lug 314 f provides a rib extending vertically andhaving a triangular cross section. A width from the tip of the rib tothe rear surface of the lug 314 f is slightly greater than alongitudinal size of the pocket 111 k; accordingly, the tip of the ribmay be crushed when the lug 314 f is set within the pocket 111 k, whichmay push the optical receptacle 314 against the rear wall 111 j.

The receptacle housing 314 a further provides a plurality ofprotrusions, 314 n and 314 m, not only in the periphery of the opening314 h and the step 314 k but in the top and bottom surfaces of thereceptacle housing 314 a. When the first housing 110 a and the secondhousing 110 b are assembled with others as putting the opticalreceptacle 314 therebetween, the tip of respective protrusions 314 n maybe crushed, which may reliably hold the optical receptacle 314 betweenthe housings, 110 a and 110 b. Moreover, when the face cover 12 is setin the front wall 110 d of the first housing 110 a as pushing theoptical receptacle 314 against the rear wall 111 j, the tip of theprotrusions 314 m may be crushed, which may reliably fix the opticalreceptacle 314 in the center area 111 a.

In the embodiments of the optical receptacle thus described, the lugsare each formed in a position measured from the front surface of thereceptacle housing which is common to both lugs in respective sidewalls. However, the lugs in respective side walls may be arrangeddiagonally and the pockets 111 k corresponding to the lugs may be alsoformed diagonally in respective side walls 111 i. The diagonalarrangement of the lugs, 114 f, 214 f, and 314 f and the pockets 111 kmay protect the optical receptacle, 114, 213 and 314, from being setreversely. Moreover, the conductive sheet, 14 and 114, described aboveis exemplarily shown by a metal plate; however, the conductive sheet maybe a type of double layers of a rubber and a metal sheet. In such anexample, the metal sheet is put between the optical receptacle 114, 214,and 314, and the rear wall 111 j such that the metal sheet comes incontact with the rear wall 111 j.

Next, a mechanism of the screw latch 16 will be described. As alreadydescribed, the face cover 12 is fixed to the first housing 10 a withscrews so as to expose the cavity of the optical receptacle 14 from theoptical port 12 a of the face cover 12 as pushing the optical receptacle14 against the rear wall 11 j of the first housing 10 a.

FIG. 27 shows the screw latch 16 according to an embodiment of thepresent invention. The screw latch 16 includes a bar portion 16 c with aknob 16 a in one end thereof and a thread 16 b in the other end which isengaged with the tapped hole of the host connector 3 a. The knob 16 a isprovided for the manual operation for the optical transceiver 1. The barportion 16 c further provides a ringed groove 16 e and a flange 16 f ina side of the knob 16 a. A coil spring is set between the ringed groove16 e and the flange 16 f. The screw latch 16 is set in the side space 10g formed in the rib 10 c of the first housing 10 a.

FIG. 28 magnifies a front portion of the first housing 10 a. The sidegroove 10 g includes a space 11 p with a width greater than restportions of the groove 10 g. The space 11 p receives the portion betweenthe ringed groove 16 e and the flange 16 f in which the coil sprig isset. The space 11 p provides a front step 11 x and a rear step 11 y. Thefront step 11 x faces the front surface of the flange 16 e, while, therear step 11 y abuts against the coil spring. The coil spring pushes thescrew latch 16 forward; accordingly, the knob 16 a is pushed forward bythe action to release the engagement of the thread 16 b with the tappedhole of the host connector, which makes it clear that the opticaltransceiver 1 is released from the host system.

In a preferred modification, the screw latch 16 may provide a washer inthe side of the flange 16 f to prevent the coil spring from rotatingoccurred in the rotation of the screw latch 16 to engage it with thetapped hole of the host connector 3 a. Specifically, the space 11 p isformed in rectangular and the plane shape of the washer may berectangular, which prevent the washer from rotating in the space 11 p.

Referring to FIG. 28 again, the first housing 10 a provides the frontwall 10 d with a lateral groove 11 r in the front surface thereof, whichmay be referred in FIG. 21B. The groove 11 r extends from the center,where the optical receptacle 14 is to be installed, to the side close tothe knob 16 a. A latch bar 13 is set within the groove 11 r. FIG. 29shows the latch bar 13 made of metal plate and includes a band portion13 a, a hooked portion 13 b, and a pushed portion 13 c. The pushedportion 13 c is bent rearward, while the hooked portion 13 b is steppedforward.

The latch bar 13 may further include an elastic portion 13 d in themiddle of the band portion 13 a. The elastic portion 13 d extends up anddown and causes a lateral pressure to the latch bar 13, that is, thelatch bar 13 is pushed toward the optical receptacle 14 by the elasticportion 13 d. The front wall 10 d of the first housing 10 a may furtherprovide in the front surface thereof another groove 11 s extending upand down to receive the elastic portion 13 d of the latch bar 13. Theelastic portion 13 d may be bent in the groove 11 s.

On the other hand, the optical receptacles shown in FIGS. 22A to 22C,26A and 26B, may provide cuts, 114 p, and 314 p, in the side wallthereof to pass the latch bar 13. The pushed portion 13 c of the latchbar 13 protrudes into the cavity of the optical receptacle, as passingthe band portion 13 a thereof through the cut of the optical receptacle.The pushed portion 13 c is bent rearward in the cavity.

FIG. 30A is a cross section of the front portion of the opticaltransceiver 1 when the optical transceiver 1 is free from the hostsystem 2, that is, the screw latch 16 is disengaged with the tappedhole. FIG. 30B is a front view of the optical transceiver 1, whichremoves the face cover 12 to show the front wall 10 d thereof. Asdescribed above, the latch bar 13 is pushed toward the opticalreceptacle 14 by the elastic force of the elastic portion 13 d. When thecavity 14B is free from an external optical connector 100, that is thecavity 14B does not receive the external connector 100, the latch bar 13in the pushed portion 13 c protrudes into the cavity 14B.

Under the arrangement described above when the screw latch 16 is freefrom the tapped hole, the insertion of the external connector 100 intothe cavity 14B may be prevented because the tip of the hooked portion 13b abuts against the screw latch 16 and the pushed portion 13 c is leftwithin the cavity 14B. On the other hand, when the screw latch 16 isengaged with the tapped hole, the tip of the hooked portion 13 b isaligned with the ringed groove 16 e of the screw latch 16. Inserting theexternal connector 100 into the cavity 14B, the external connector 100pushes the pushed portion 13 c of the latch bar 13 and the tip of thehooked portion 13 b thereof may be escaped into the ringed groove 16 e.Moreover, when the tip of the hooked portion 13 b is escaped into theringed groove 16 e, the screw latch 16 is unable to be disengaged withthe tapped hole, because the hooked portion 13 b prevents the screwlatch 16 from moving frontward.

Accordingly, the optical transceiver 1 of the present embodiment, whenthe external connector 100 is mated with the optical receptacle 14,which means that the optical transceiver 1 is engaged with the hostsystem 2 by screwing the latch bar 16 with the tapped hole of the hostsystem 2, may prevent two cases, one of which is that the externalconnector is unable to be inserted into the optical receptacle 14 whenthe optical transceiver 1 is free from the host system 2, and the othercase is that the optical transceiver 1 is unable to be extracted fromthe host system 2 when the external connector 100 is engaged with theoptical receptacle 14.

The elastic portion 13 d shows a function of a leaf spring, that is, asshown in FIG. 30D, the elastic portion 13 d is bent by the insertion ofthe external connector 100 into the optical receptacle 14, and theelastic portion 13 d pushes back the latch bar 13 as the cavity 14Bbecomes vacant. Although the figures only show a case that the latch bar13 has the bent pushed portion 13 c, the pushed portion 13 c may has anarched shape.

Second Embodiment

Next, a process to assembly the optical transceiver 1 according to thesecond embodiment of the present invention will be described in detail.The process described below assumes a condition that the opticaltransceiver 1 provides the housing 100, the front tray 124, the reartray 136, and the inner connector 126 of the second embodiment.

The process first installs the rear tray 136 on the fourth section R₄,the optical multiplexer 20 and the optical demultiplexer 22 onrespective positions. Then, the process wires the inner fibers, F₂ toF₈.

As shown in FIG. 31A, setting the inner fiber F₆ extended from theoptical multiplexer 20 within the grooves, G₂ and G₄, formed in thesections, R₂ and R₃, of the transmitter side, the inner fiber F₆ isextended to the fourth section R₄. Guiding the fiber F₆ along the reartray 136 to turn to the receiver side, and drawing along the side of thereceiver side, the fiber F₆ reaches the first section R₁. Eaves 136 cprovided in the rear tray 136 may prevent the fiber F₆ from strayingout. Various eaves 136 c in the rear tray 136 may be optionally useddepending on the surplus length of the inner fiber F₆.

As shown in FIG. 31B, setting the inner fiber F₈ extended from theoptical demultiplexer 22 within the grooves, G₂ and G₄, formed in thesections, R₂ and R₃, of the receiver side, the inner fiber F₈ isextended to the fourth section R₄. Guiding the fiber F₈ along the reartray 136 to turn to the transmitter side, and drawing along the side ofthe transmitter side, the fiber F₈ reaches the first section R₁. Eaves136 c provided in the rear tray 136 may prevent the fiber F₈ fromstraying out. Various eaves 136 c in the rear tray 136 may be optionallyused depending on the surplus length of the inner fiber F₈.

The inner fibers F₆ and F₈ may be installed with a ferrule 20 b, a coilspring 20 a and a flange 20 d in advance to the wiring thereof.

Next, the process may draw the inner fiber F₂ extended from the opticalmultiplexer 20 within the grooves, G₂ to G₆, to the fourth section R₄ asshown in FIG. 31C. Guiding the fiber F₂ along the rear tray 136 towardthe receiver side, then the fiber F₂ is set in one of the grooves, G₂Sor G₂L, corresponding to the type of the optical receptacle 14 to bemounted in the center area 111 a. The eaves 136 c in the rear tray 136may guide the inner fiber F₂ and prevent the fiber F₂ from straying out.Various eaves 136 c may be also optionally used depending on a length ofthe fiber F₂.

Finally, as shown in FIG. 31D, the inner fiber F₄ output from theoptical demultiplexer 22 is guided in the grooves, G₂ to G₆, in secondand third sections, R₂ and 3, to the front end of the fourth section R₄.In the fourth section R₄, the inner fiber F₄ is bent along the rear tray136 toward transmitter side, and is guided in one of the grooves, G₂Sand G₂L, depending on the type of the optical receptacle 14 to thecenter area 111 a. The eaves 136 c may also prevent the inner fiber F₄from straying out. Various eaves 136 c may be optionally used dependingon a length of the fiber F₄.

The optical receptacle 114 may build, in advance to the wiring of theinner fibers, F₂ and F₄, the receptacle housing 114 a and the sleeveholder 114 b with the conductive sheet 114 c. Subsequent to the wiringof the inner fibers, F₂ to F₈, the sleeve 20 c is inserted into theopening 114 h in the rear wall 114 e of the optical receptacle 114through the opening 114 r in the conductive sheet 114 c. The opticalreceptacle 114, thus assembled with the sleeves, 20 c and 22 c, aremounted on the center area 111 a of the first housing 110 a. In thisprocess, the lugs 114 f prepared in the side wall of the opticalreceptacle 114 are set within the pocket 111 k.

Then, the front tray 126 is fixed on the second section R₂. The innerfibers F₆ wired in the side end of the receiver side are drawn under theceiling 124 s of the front tray 124, drawn under the front eaves 124 xto the transmitter side, and finally guided in respective slots 124 a ofthe front tray 124. Each fiber F₆ is guided by the guide walls, 124 tand 124 u, the front wall 124 v, the front eaves 124 x, and slot eaves124 d. While, the other inner fibers F₈, which are wired in the side ofthe transmitter side, are drawn under the ceiling 124 s, under the fronteaves 124 x to the receiver side, and finally guided to respective slots124 a. Each fiber F₈ is also guided by the guide walls, 1241 and 124 u,the front wall and eaves, 112 v and 124 x, and respective slot eaves 124d. Thus, the inner fibers, F₆ and F₈, may be wired without straying out,as shown in FIG. 32.

Next, the process assembles the inner connectors 126 with the front tray124. Specifically, the latch finger 124 b of the front tray 124 isinserted into the groove 126 e of the inner connector 126, andtemporarily sets the end of the ferrule 20 b in a position where theinner fiber F₆ may optically couple with the OSA, 30 and 32. FIG. 33Bcorresponds to the coupling position. Then, sliding the inner connector126 frontward such that the tip of the latch finger 124 b is set in thesecond pocket 126 n, the ferrule 20 b does not interfere with theinstallation of the OSAs, 30 and 32. FIG. 33A corresponds to thisescaped position.

Next, the latch unit 128 is set in its regular position and the OSAs, 30and 32 are set in the latch unit 128, as shown in FIG. 34. In advance tothe installation of the circuit board 18, the OSAs, 30 and 32 areconnected with respective FPCs 18 d. Mounting the circuit board 118 onthe first housing 110 a, and inserting the rib 19 e of the plug board 19into the groove 10 v of the first housing 10 a, the optical andelectrical components are installed on the first housing 10 a. Inadvance to the installation of the circuit board 18, the gasket 34 b maybe set within the groove 101, and the metal cover 35 may be set in thegroove 10 v.

Sliding the inner connector 126 rearward so that the tip of the latchfinger 124 b is set in the first pocket 126 m in the groove 126 e of theinner connector 126, and engaging the projection 128 c of the latch unit128 with the opening 126 d of the inner connector 126, the tip of theferrule 20 b may come in physically contact with the stub 30 u in theOSA, 30 and 32.

Finally, the face cover 12 is fixed to the first housing 110 a asputting the optical receptacle 14 between the face cover 12 and the rearwall 111 j of the center area 111 a. Setting the other gasket 34 a inthe groove 111 m of the second housing 110 b and the other metal cover35 in the groove 11 v, and fixing the second housing 110 b to the firsthousing 110 a, the optical transceiver 1 may be completed.

1. An optical communication apparatus for a wavelength divisionmultiplex communication, comprising: a plurality of optical componentsincluding: an optical receptacle configured to couple with an externaloptical connector; a plurality of optical subassemblies, each processingan optical signal having a specific wavelength different from others;and an optical unit arranged between said optical subassemblies and saidoptical receptacle, said optical unit processing said optical signals,an electrical component including, a circuit board configured to mountan electronic circuit electrically coupled with said opticalsubassemblies; a plurality of inner fibers each coupling one of saidoptical subassemblies with said optical unit; and a housing configuredto install said optical components, said electrical component and saidinner fibers therein, wherein said housing is divided into two sections,one of which installs only said optical components, and another of whichinstalls only said electrical component, and wherein each of said innerfibers is coupled with one of said subassemblies in a pluggable form. 2.The optical communication apparatus of claim 1, wherein said innerfibers are arranged under said circuit board in said other section, andunder said optical unit in said one section.
 3. The opticalcommunication apparatus of claim 1, wherein said optical componentsfurther includes: a plurality of inner connectors each provided in anend of said inner fiber and coupled with one of said opticalsubassemblies in said pluggable form; and a front tray supports saidinner connectors and arranges said inner fibers.
 4. The opticalcommunication apparatus of claim 3, wherein said optical componentsfurther includes, a latch unit configured to arrange said opticalsubassemblies, said inner connectors being coupled with said latch unitin two positions.
 5. The optical communication apparatus of claim 4,wherein said latch unit is arranged over said inner fibers.
 6. Theoptical communication apparatus of claim 5, wherein said front tray isarranged over said inner fibers.
 7. The optical communication apparatusof claim 5, wherein said front tray provides a plurality of slots eachreceiving one of said inner fibers and having a pair of latch fingers toengage said inner connector.
 8. The optical communication apparatus ofclaim 7, wherein each of said slots of said front tray provides an eaveto prevent said inner fiber set in said slot from straying out.
 9. Theoptical communication apparatus of claim 7, wherein said front trayprovides a guide to turn said inner fibers from a longitudinal directionto a lateral direction.
 10. The optical communication apparatus of claim7, wherein said front tray, said inner connector, and said latch unitconstitute said pluggable form.
 11. The optical communication apparatusof claim 1 further comprising a rear tray arranged under said circuitboard, said rear tray guiding said inner fibers drawn from said onesection so as to head to said one section.
 12. The optical communicationapparatus of claim 11, wherein said rear tray further provides aplurality of eaves to prevent said inner fibers from straying out. 13.The optical communication apparatus of claim 1, wherein said one sectionof said housing provides a plurality of terraces for mounting saidoptical components thereon, and said another section of said housingprovides a plurality of terraces whose outer periphery defines acurvature of said inner fibers.
 14. The optical communication apparatusof claim 13, wherein said terraces provided in said other section comein contact with said electronic circuits mounted on said circuit board.15. The optical communication apparatus of claim 1, wherein said housingprovides a plurality of grooves extending from said one section to saidother section, and wherein said inner fibers are set within saidgrooves.
 16. The optical communication apparatus of claim 15, whereinsaid grooves in said one section provides a first pair of grooves and asecond pair of grooves, and wherein said first pair of grooves have adistance substantially equal to a distance between two fibers set in aSC-type optical receptacle, and said second pair of grooves have adistance substantially equal to a distance between two fibers set in anLC-type optical receptacle.
 17. The optical communication apparatus ofclaim 1, wherein said housing provides an area for mounting said opticalreceptacle, said area being partitioned from said one section by a rearwall, and wherein said optical receptacle is mounted on said area asputting a conductive sheet between said optical receptacle and said rearwall.